* {
  margin: 0;
  padding: 0;
}
li {
  list-style: none;
}
a {
  text-decoration: none;
  color: black;
}
.w {
  width: 1200px;
  margin: 0 auto;
}
.top {
  display: flex;
  justify-content: space-between;
  color: #000;
  height: 45px;
  background-color: rgba(255, 255, 255, 0.7);
  box-shadow: 0 0 15px #747474;
  position: fixed;
  width: 100vw;
}
.top .logo {
  width: 8vw;
  background-color: #422f2f;
  color: white;
  text-align: center;
  line-height: 35px;
  border-radius: 20px;
  margin: 5px;
}
.top .nav {
  width: 30vw;
}
.null_box {
  height: 70px;
}
.box {
  width: 860px;
  background-color: rgba(255, 255, 255, 0.5);
  box-shadow: 0 8px 25px 0 rgba(148, 146, 146, 0.7);
  margin: 0 auto;
  padding: 45px;
}
.box:hover {
  box-shadow: 0 8px 25px 0 rgba(0, 0, 0, 0.7);
  transition: all 0.5s;
}
pre {
  background-color: #efefef;
}
